AbstractThirty bladder tumours of various stages and grades were examined for the presence of A.B.O. (H) cell surface antigen using specific red cell adherence (SCRA) technique. Ten patients with stage A disease and low grade tumour (grade I) retained the antigens, whereas all patients with high stage disease (B,C,D) and high grade tumours showed absence of antigen. When these data were correlated with recurrence pattern and metastasis or invasion rate, patients who did not show the antigen at the initial visit developed metastases and had poor prognoses. The patient who had expressed the antigen by positive SCRA had fewer recurrences and a longer tumour‐free interval Hence if SCRA is done in all bladder tumours at the initial visit and at subsequent follow‐up, it can be used as a biological mar